It is known to cool combustion products (for example cement clinker) by a layer of the combustion products being conveyed on a grate, while cooling air is forced through the grate and the product layer. In a known type of such a cooler (EP-B-676031; EP-A-718578; WO-A-8401616), a stationary grate surface is used, over which the product bed is moved by means of a conveyor. The latter consists of a pair of endless conveyor chains which are arranged on both sides of the grate and between them carry drivers which lie transversely to the conveying direction and drive the products lying between and above them in the conveying direction, that is to say in the longitudinal direction of the cooler. The driver beams are surrounded by hot products and are therefore exposed to wear. This applies particularly to the initial region of the cooler, where the hot products to be cooled, emerging directly from the furnace, meet the drivers.
When the stream of products to be fed onto the grate meets the conveying grate and its drivers directly, high wear and high mechanical stress occur. In order to avoid this, there may be provision (EP-B-676031, EP-A-718578) for the combustion products first to fall onto a stationary surface which consists of grate plates with air throughflow and from which the products are moved, even without additional conveying means, towards the start of the conveying grate solely by virtue of an inclination of this surface. In order to ensure that the products have a dwell time sufficient for precooling, the surface is inclined only slightly and has a considerable length. This presents problems in terms of a uniform operation of the cooler, particularly in the case of difficult products which tend to cake on and cake together.
In another known cooler of the type just described (EP-A-726440) the grate and the drivers are protected in that, before the feed of the products to be cooled, a layer of already cooled products returned from the end of the grate to the start is fed. The grate and the drivers are protected, by the cool product layer enveloping them, from the hot product layer located above it. The outlay for returning the cooled products and for conveying double the quantity of products on the grate is high.